Kicker magnets are

dipole magnet A dipole magnet is the simplest type of magnet. It has two poles, one north and one south. Its magnetic field lines form simple closed loops which emerge from the north pole, re-enter at the south pole, then pass through the body of the magnet. T ...

s used to rapidly switch a

particle beam A particle beam is a stream of charged or neutral particles. In particle accelerators, these particles can move with a velocity close to the speed of light. There is a difference between the creation and control of charged particle beams and neu ...

between two paths. Conceptually similar to a

railroad switch A railroad switch (), turnout, or ''set ofpoints () is a mechanical installation enabling railway trains to be guided from one track to another, such as at a railway junction or where a spur or siding branches off. The most common ty ...

in function, a kicker magnet must switch on very rapidly, then maintain a stable magnetic field for some minimum time. Switch-off time is also important, but less critical. An injection kicker magnet merges two beams incoming from different directions. Most commonly, there is a beam circulating in a

synchrotron A synchrotron is a particular type of cyclic particle accelerator, descended from the cyclotron, in which the accelerating particle beam travels around a fixed closed-loop path. The magnetic field which bends the particle beam into its closed p ...

, in the form of a particle train which only partially fills the arc. As soon as the circulating particle train has passed the kicker, it is switched on so that an additional batch of particles may be

append In computer programming, append is the operation for concatenating linked lists or arrays in some high-level programming languages. Lisp Append originates in the Lisp programming language. The append procedure takes zero or more (linked) lists a ...

ed to the train. The magnet must then be switched off in time to not affect the head of the train when it next rounds the synchrotron. An ejection kicker magnet does the opposite, diverting a circulating beam so it leaves the synchrotron. Almost always, an ejection kicker is used to eject the entire particle train, emptying the synchrotron. This means that it has the entire tail-to-head gap in the synchrotron to function, and the switch-off time is essentially irrelevant. However, it must hold a stable field for longer (one full rotation of the synchrotron), and must generate a stronger magnetic field, as it is used to eject a higher energy beam that has been accelerated in the synchrotron. The magnets are powered by a high voltage (usually in the range of tens of thousands of

volt The volt (symbol: V) is the unit of electric potential, electric potential difference (voltage), and electromotive force in the International System of Units (SI). It is named after the Italian physicist Alessandro Volta (1745–1827). Defi ...

s) source called a

power modulator Power most often refers to: * Power (physics), meaning "rate of doing work" ** Engine power, the power put out by an engine ** Electric power * Power (social and political), the ability to influence people or events ** Abusive power Power may ...

which uses a

pulse forming network A pulse-forming network (PFN) is an electric circuit that accumulates electrical energy over a comparatively long time, and then releases the stored energy in the form of a relatively square pulse of comparatively brief duration for various puls ...

to produce a short pulse of current (usually in the range of a few

nanosecond A nanosecond (ns) is a unit of time in the International System of Units (SI) equal to one billionth of a second, that is, of a second, or 10 seconds. The term combines the SI prefix ''nano-'' indicating a 1 billionth submultiple of an SI unit ( ...

s to a

microsecond A microsecond is a unit of time in the International System of Units (SI) equal to one millionth (0.000001 or 10−6 or ) of a second. Its symbol is μs, sometimes simplified to us when Unicode is not available. A microsecond is equal to 1000 n ...

and thousands of

ampere The ampere (, ; symbol: A), often shortened to amp,SI supports only the use of symbols and deprecates the use of abbreviations for units. is the unit of electric current in the International System of Units (SI). One ampere is equal to elect ...

s in amplitude). The current produces a

magnetic field A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to ...

in the magnet, which in turn imparts a

Lorentz force In physics (specifically in electromagnetism) the Lorentz force (or electromagnetic force) is the combination of electric and magnetic force on a point charge due to electromagnetic fields. A particle of charge moving with a velocity in an elect ...

on the particles as they traverse the magnet's length, causing the beam to deflect into the proper trajectory. Because a kicker magnet applies a particular lateral

impulse Impulse or Impulsive may refer to: Science * Impulse (physics), in mechanics, the change of momentum of an object; the integral of a force with respect to time * Impulse noise (disambiguation) * Specific impulse, the change in momentum per uni ...

to the beam, to achieve a fixed deflection angle the strength of the kick must be accurately matched to the momentum of the particles. This is part of the power modulator's job.

References

* * Accelerator physics {{Accelerator-stub